CN108120382A - For measuring the SPR differential phae measuring methods of nano level metal film thickness - Google Patents
For measuring the SPR differential phae measuring methods of nano level metal film thickness Download PDFInfo
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- CN108120382A CN108120382A CN201611065308.XA CN201611065308A CN108120382A CN 108120382 A CN108120382 A CN 108120382A CN 201611065308 A CN201611065308 A CN 201611065308A CN 108120382 A CN108120382 A CN 108120382A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y35/00—Methods or apparatus for measurement or analysis of nanostructures
Abstract
The invention discloses a kind of for measuring the SPR differential phae Method for Phase Difference Measurement of nanoscale double-layer metal film thickness, step 1：Establish thickness of metal film functional relation；Step 2：It sets one group of incidence angle and changes magnitude, select a value initial incidence angle and change magnitude, light beam 1,2 incides into prism-type SPR metallic films interface simultaneously；Step 3：Obtain the interference fringe image of coating film area light beam 1 and light beam 2；Step 4：Obtain the interference fringe image of non-coating film area light beam 1 and 2；Step 5：The light beam 1,2 that step three and four is obtained is compared with the interference image of non-coating film area in plated film, calculates respectively, obtains differential values；Step 6：Step 3 is repeated to five, matched curve is obtained, and acquires the matched curve slope；Step 7：Determine institute's metal-coated films thickness.Present invention has the advantages that：Realize non-contact, the high-acruracy survey to nanoscale single layer metal firms thickness, the simple in measurement system structure is easy to operation.
Description
Technical field
It is more particularly to a kind of thin for measuring nano level metal the present invention relates to a kind of measuring method of thickness of metal film
The SPR differential phae measuring methods of film thickness.
Background technology
As thin film technique is in microelectronics, photoelectron, aerospace, bioengineering, weaponry, Food Science, medical treatment
The extensive use in the fields such as instrument and high molecular material, thin film technique have become in current Technological research and field of industrial production
The rapid development of research hotspot, particularly nano-level thin-membrane technology has directly influenced developing direction and the people of science and technology
Life style.And continuously improving and rapidly developing for film fabrication techniques also proposes the various parameters of film higher want
It asks, such as the thickness of film and refractive index parameter and reflection, transmission, absorption characteristic etc., wherein film thickness is film design
One of key parameter in being manufactured with technique, it has for the optical characteristics of film, mechanical characteristic and electromagnetic property etc. determines
The effect of property, therefore can accurately detect film thickness and have become a kind of vital technology.
At present, mainly angled type, spectral type and phase type, wherein phase type SPR are passed the modulation type of SPR sensorgram technology
Sense technology possesses higher sensitivity, has a clear superiority.Such as Chinese Patent Application No. is 201310137996.6, is disclosed
A kind of SPR phase measuring method for being used to measure nano level metal film thickness, the method can avoid ambient light to measurement accuracy
Caused by influence, but there is also the deficiencies of sensitivity is low, dynamic range is small.In many scientific and technical literatures, mention using differential
The mode of measurement, it is differential in addition to improve the indexs such as instrument or the non-linear of system, resolution ratio, sensitivity and dynamic range
Measurement can also eliminate the common mode interference in measuring system, and therefore, the present invention is combined using variate with SPR phase modulation
Method directly to measure the thickness of metallic film, provide a kind of new approaches to measure nano level metal film thickness.
The content of the invention
The technical problems to be solved by the invention, which are to provide, a kind of has non-contact, high-precision, simple in structure, easy to operation
Measurement nano level metal film thickness method.
In order to solve the above-mentioned technical problem, the technical solution adopted by the present invention is：One kind is thin for measuring nano level metal
The SPR differential phae measuring methods of film thickness, step are as follows：
Step 1：Establish thickness of metal film dm and the functional relation formula of slope k：The formula is according to selected incidence angle
The value of the value range of variation Δ θ and incident central angle θ 0 is calculated when obtaining each thickness, one group with by incidence angle variation
Δ θ, which is independent variable, this group of incidence angle variation Δ θ is drawn by dependent variable of corresponding differential values ΔΦ corresponds to differential values
The relation curve of ΔΦ is fitted the slope k of this relation curve, establishes thickness of metal film dm and the corresponding theoretical pass of slope k
It is curve, and is fitted and solves thickness of metal film dm and the functional relation formula dm=f (k) of slope k；Step 2：According to step
The value range of incidence angle variation Δ θ described in rapid one within its scope, sets one group of incidence angle variation Δ θ value, and
One group of incidence angle is changed in magnitude herein, is selected a value and is changed magnitude as initial incidence angle, light beam 1 with θ 0+ Δs θ, light beam 2 with
The angle of θ 0- Δs θ incides into the metallic film interface of prism-type spr sensor simultaneously；Step 3：Entering according to step 2
Mode is penetrated, obtains prism-type spr sensor coating film area light beam 1 and 2 respective interference fringe image of light beam；Step 4：According to
Incidence described in step 2 obtains the non-coating film area light beam 1 of prism-type spr sensor and 2 respective interference fringe of light beam
Image；Step 5：The light beam 1 and light beam 2 that step 3 and step 4 are obtained are in the interference pattern of coating film area and non-coating film area
As being compared, calculating respectively, light beam 1 and light beam 2 are respectively obtained in the TM polarized waves of coating film area and the phase of TE polarized waves
Variable quantity difference DELTA δ r1With Δ δ r2, by Δ δ r1With Δ δ r2Subtract each other, obtain differential values ΔΦ；Step 6：According to step 2, according to
It is secondary to change the value of Δ θ, and repeat step 3 to step 5, obtain one group it is corresponding differential with incident angle variation Δ θ
It is worth ΔΦ, one group (Δ θ, ΔΦ) of gained is carried out curve fitting, and acquires the slope k of the matched curve；Step 7：It will
The slope k of experiment curv obtained by step 6, substitutes into the functional relation formula d in step 1mIn=f (k), you can determine that SPR is passed
The thickness of sensor institute metal-coated films.
The incident central angle θ of the step 10Within SPR resonance angle ± 1 °, the incidence angle of the step 1 becomes value
The value range of momentum Δ θ is -0.1 °~0.1 °；The different metal film thickness d of the step 1mCorresponding differential values ΔΦ with
The theory curve basic parameter of the slope of curve k of incidence angle variation Δ θ is：1. incident angle θ0, 2. incidence angle change
Momentum Δ θ, 3. Refractive Index of Glass Prism np, the 4. permittivity ε of metallic filmm, the 5. permittivity ε of aira, 6. laser enter
Penetrate light wavelength lambda；The step 2 makes light beam 1 with θ0+ Δ θ, light beam 2 are with θ0The angle of-Δ θ incides into prism-type spr sensor
Metallic film interface, refer to that a hot spot part for light beam 1 and light beam 2 is in the plated film area of spr sensor, a part is in
The non-plated film area of spr sensor, and the hot spot of light beam 1 and light beam 2 is incident to the different position at interface；The step 3 is by light
Beam 1, light beam 2 incide into prism-type spr sensor coating film area reflected light be respectively divided into TM1 polarized waves and TE1 polarized waves,
TM2 polarized waves and TE2 polarized waves, TM1 polarized wave of the light beam 1 using in reflected light is as measurement light, and TE1 polarized waves are as reference
Light, TM2 polarized wave of the light beam 2 using in reflected light are used as measurement light, TE2 polarized waves with reference to light, then, make the TM1 of light beam 1
Polarized wave and TE1 polarized waves generate interference fringe after interference system and polarizer, make the TM2 polarized waves of light beam 2 and TE2 polarizations
Ripple generates interference fringe after interference system and polarizer, records two interference images respectively；The step 4 is by light beam 1, light
The reflected light that beam 2 incides into the non-coating film area of prism-type spr sensor is respectively divided into TM1 polarized waves and TE1 polarized waves, TM2 are inclined
Vibration wave and TE2 polarized waves, TM1 polarized wave of the light beam 1 using in reflected light are used as measurement light, TE1 polarized waves with reference to light, light beam
The 2 TM2 polarized waves using in reflected light are used as measurement light, TE2 polarized waves with reference to light, then make light beam 1 TM1 polarized waves and
TE1 polarized waves generate interference fringe after interference system and polarizer, make light beam 2 TM2 polarized waves and TE2 polarized waves through interference
Interference fringe is generated after system and polarizer, records two interference images respectively；The step 5 is to obtain step 3 and step 4
The light beam 1 and the coating film area of light beam 2 taken is compared, calculates and handles with the interference image of non-coating film area respectively, respectively
It obtains in two width interference images of light beam 1 and light beam 2 in the offset of interference fringe and interference image between adjacent interference fringe
Every amount, the TM1 polarized waves of coating film area light beam 1 and the phase changing capacity difference DELTA δ of TE1 polarized waves are thus calculatedr1And plating
The TM2 polarized waves of diaphragm area light beam 2 and the phase changing capacity difference DELTA δ of TE2 polarized wavesr2, by Δ δr1With Δ δr2Subtract each other, obtain
Differential values ΔΦ.
The interval of one group of incidence angle variation Δ θ value of setting of the step 2 is at least 0.02 °.
The step 3 incides into the reflected light of prism-type spr sensor coating film area, to incide into prism-type SPR sensorgram
The light at device prism-metallic film interface；The step 4 incides into the reflected light of the non-coating film area of prism-type spr sensor,
To incide into the light of prism-type spr sensor prism-Air Interface；The step 6 is opened from initial incidence angle variation Δ θ
Begin, change the value of incident angle variation Δ θ successively, variation order should be according to one group of incidence angular variable set by step 2
Amount；The step 7 is by the slope k of experiment curv obtained by step 6, substitutes into the theory function relation formula given by step 1
dm=f (k) determines the thickness of spr sensor institute metal-coated films.
The metallic film is gold, silver, copper, aluminium, platinum, titanium, nickel, chromium metallic film.
The measurement range of the thickness of metal film is 0-100nm, measurement resolution 0.1nm.
Light beam 1 described in step 2 is with θ0+ Δ θ, light beam 2 are with θ0- Δ θ can be set to symmetrical direction or same with side direction
When incide into the metallic film interface of prism-type spr sensor.Two-beam can the left and right sides it is symmetrical incident, can also be in one side
Incidence, as long as meeting required angle.
The step 2 makes light beam 1 with θ0+ Δ θ, light beam 2 are with θ0The angle of-Δ θ incides into prism-type spr sensor
The different position at metallic film interface is two-beam or multi-beam.
The beneficial effects of the invention are as follows：The present invention is based on single-layer metal film constituent prisms type spr sensor and differential phase
Position modulator approach, TM polarized waves and the TE that the reflected light of coating film area is symmetrically incided into using laser interference method two beams of acquisition are inclined
Vibration wave phase difference by the method for variate, realizes and non-contact, the high-precision of nanoscale single layer metal firms thickness is surveyed
Amount, and it is the simple in measurement system structure, easy to operation.
Description of the drawings
Fig. 1 is the basic structure schematic diagram for the prism-type spr sensor that the present invention is coated with metal film,
Fig. 2 (a) is the phase difference δ of the reflected beams TM ripples and TE ripples in SPR phase methodrBecome with incidence angle variation Δ θ
The relation curve of change,
Fig. 2 (b) is the relation curve that differential values ΔΦ changes with incidence angle variation Δ θ in SPR differential phae methods,
ΔΦ corresponds to incident angle variation Δ when Fig. 3 (a) is differential values difference golden film thickness (30-50nm) of the present invention
The theory curve of θ,
ΔΦ corresponds to incident angle variation Δ when Fig. 3 (b) is differential values difference golden film thickness (65-85nm) of the present invention
The theory curve of θ,
Fig. 4 (a) is golden film thickness d of the present inventionm(0-50nm) corresponds to differential values ΔΦ and incident angle variation Δ θ's
The theory curve of slope of curve k,
Fig. 4 (b) is golden film thickness d of the present inventionm(65-100nm) corresponds to differential values ΔΦ and incident angle variation Δ θ
Slope of curve k theory curve,
Fig. 5 is the implementation steps that the present invention is used to measure the SPR differential phae measuring methods of nano level metal film thickness
Flow chart,
Fig. 6 be the present invention is based on SPR differential phaes detection method measure thickness of metal film experimental provision schematic diagram,
Fig. 7 is the schematic diagram that prism-type spr sensor of the present invention is placed on XYZ D translations guide rail and corner platform,
Fig. 8 is the one-dimensional space position view of fringe intensity in interference image of the present invention.
Specific embodiment
The present invention is described in further detail with reference to the accompanying drawings and detailed description：
Surface plasma body resonant vibration (Surface Plasmon Resonance, SPR) effect is a kind of special physics
Optical phenomena.Using light wave when being totally reflected in medium and metallic interface generated evanescent wave, metal can be triggered
The collective oscillation of surface free electron, so as to form surface plasma wave (Surface Plasmon Wave, SPW), it
Magnetic vector is oriented parallel to the interface of medium and metal, and magnetic field intensity reaches maximum at interface and in two media
Middle presentation exponential decay trend, when incident light wave vector is equal to surface plasma wave wave vector, you can excitation SPR effects.Mesh
Before, mainly angled type, spectral type and phase type, wherein phase type SPR sensorgram technology possess the modulation type of SPR sensorgram technology
Higher sensitivity, has a clear superiority, but finds phase difference and film thickness relation there are still nonlinear problem in studying, this causes
The sensitivity, dynamic range and measurement resolution of this method are largely there are still the potentiality of raising, in many science and technology texts
In offering, the mode using variate is mentioned, to improve instrument or the non-linear of system, resolution ratio, sensitivity and dynamic
The indexs such as scope, in addition variate can also eliminate the common mode interference in measuring system, and therefore, the present invention utilizes variate
The thickness of metallic film is directly measured with the method that SPR phase modulation is combined, is carried for measurement nano level metal film thickness
For a kind of new approaches.
It is the basic structure schematic diagram of prism-type spr sensor as shown in Figure 1, incident light E is incident with SPR effects resonance angle
To after the 602 interface excitation SPR effects of prism 601- metallic films of prism-type spr sensor 6, TM polarized waves in reflected light E '
Phase can change with the difference of thickness of metal film, and then unobvious, the two are poor for the phase place change degree of TE polarized waves
It is different very big, therefore using TM polarized waves as measurement light, TE polarized waves are used as the difference with reference to both light, calculating phase changing capacity.
According to Fresnel formula, the reflectance factor r of prism-type double-layer metal film spr sensor as shown in Figure 1 and reflection
Phase δrExpression formula be
In formula
I, j represents p, m, a respectively, and wherein p represents prism, and m represents 602 layers of metallic film, and a represents air, npFor prism
Refractive index, λ are lambda1-wavelength, and θ is incident angle, dmAnd εmFor 601 layers of thickness and dielectric constant of metallic film, rpmFor rib
The reflectance factor of 602 layers of interface of mirror and metallic film, rmaFor 602 layers of metallic film and the reflectance factor of air interface, kew
For the wave vector of evanescent wave.
For spr sensor, TM polarized waves and the corresponding phase of TE polarized waves can be acquired by above formula respectively
Variable quantity δr TMAnd δr TE, the two subtracts each other the phase changing capacity difference DELTA δ that can acquire TM polarized waves and TE polarized wavesr, from formula
It can be seen that the value is subject to the joint effect of thickness of metal film and incident angle.
According to above-mentioned formula, you can be finally inversed by the thickness of metallic film, here it is SPR phase detection methods to measure metallic film
The basic principle of thickness.The present invention is exactly on the basis of SPR phase mensuration, by way of variate, is received to measure
The thickness of meter level metallic film, the principle of differential type SPR phase detection method measurement thickness of metal film are as follows.
In the approximate angle that evanescent wave and surface plasma-wave (SPW) resonate, choose an incidence angle and be used as incidence
Angle θ0If incidence angle is compared with θ0Variation for Δ θ, then compared with θ0The angle of incidence values for increasing one side is θ0+Δ
θ, and compared with θ0The angle of incidence values for reducing one side is θ0-Δθ.To TM components and TE component phase difference variable quantity difference DELTAs δr
In θ0Place carries out Taylor expansion, as follows：
Δδ1v(θ0+ Δ θ, dm)=a0+a1Δθ+a2Δθ2+a3Δθ3+a4Δθ4+a5Δθ5+…
Δδ2v(θ0- Δ θ, dm)=a0-a1Δθ+a2Δθ2-a3Δθ3+a4Δθ4-a5Δθ5+…
Wherein：
a0=Δ δr(θ0,dm), a1=Δ δ 'r(θ0,dm), a2=Δ δ "r(θ0,dm)/2！,
a3=Δ δ " 'r(θ0,dm)/3！...
The differential values ΔΦ of the two is：
ΔΦ(θ0+ Δ θ, dm)=Δ δ1v(θ0+ Δ θ, dm)-Δδ2v(θ0- Δ θ, dm(a of)=21Δθ+a3Δθ3+a5Δθ5
+…)
From above formula as it can be seen that SPR differential phaes method can eliminate the even order terms in former SPR phase method measurement model, at the same it is sensitive
Degree is doubled.We can intuitively paired observation SPR differential phaes method exists compared with SPR phase method from data and picture
Significantly improving in sensitivity, we are given below parameter, and the wavelength of light source output is 632.8nm, Refractive Index of Glass Prism 1.51,
Metallic film uses golden film (in corresponding diagram 1 602 layer) of the dielectric constant for -10.7+0.8i, thickness 50nm, incident central angle
θ0=43.9 °, (i.e. for SPR phase method, incidence angle is for -0.1 °~0.1 ° for the value range of incidence angle variation Δ θ
43.8 °~43.9 °), Fig. 2 (a) is the phase difference δ of the reflected beams TM ripples and TE ripples in SPR phase methodrWith incidence angle variation
The relation curve of Δ θ variations, Fig. 2 (b) are the pass that differential values ΔΦ changes with incidence angle variation Δ θ in SPR differential phae methods
It is curve, in the case where the value range value of lower incidence angle variation Δ θ is identical, phase difference δrBecome 68 ° from 120 °,
Variable quantity is 52 °；ΔΦ becomes -53 ° from 53 °, and variable quantity is 103 °, it is seen that the sensitivity of SPR differential phae methods is compared to SPR
Phase method improves one times.
SPR differential phae methods are incident simultaneously using two light beams, incidence angle when making the light beam 1 incide on golden film film
For θ0+ Δ θ, incidence angle when light beam 2 is incided on golden film film are θ0- Δ θ obtains the reflected light of light beam 1 and light beam 2 at this time
The phase difference δ of the TE ripple and TM ripple caused by film thickness in beam1rWith Δ δ2r, by Δ δ1rWith Δ δ2rDifferential processing is carried out,
Differential values ΔΦ is obtained, passes through identical processing method, the value of change Δ θ, you can obtain one group of (ΔΦn, Δ θn), we
It can (Δ θs a series of according to thisn, ΔΦn) value, the relation curve of differential values ΔΦ and incidence angle variation Δ θ is drawn out, and is intended
Close out slope of a curve k, we by theoretical calculation, differential values ΔΦ when can obtain different metal film thickness with it is incident
The slope k of the relation curve of angular variable amount Δ θ, and then can be fitted to obtain thickness of metal film dmWith pair of slope of a curve k
It should be related to dm=f (k), in this way, as our a selected incident central angle θ0When, we can pass through differential values ΔΦ and incidence
The slope k of the relation curve of angular variable amount Δ θ, to determine the thickness of metallic film.
He-Ne laser of the output wavelength for 632.8nm is used in the embodiment of the present invention, prism material is BK7 glass,
Refractive index is 1.51, and metallic film uses golden film (in corresponding diagram 1 602 layer) of the dielectric constant for -10.7+0.8i, incident center
Angle θ0=43.9 °, the value range of incidence angle variation Δ θ is -0.1 °~0.1 °, at intervals of 0.01 °, is illustrated in figure 3 not
Under stack pile, theory curve that differential values ΔΦ changes with incidence angle variation Δ θ, it can be seen from the figure that different-thickness
Lower differential values ΔΦ is linear with incidence angle variation Δ θ, even if thicknesses of layers changes 1nm, relation curve also has
There is good discrimination, we can fit different film thickness dmWhen, the song of differential values ΔΦ and incidence angle variation Δ θ
Line slope k, and set up thickness dmWith the function correspondence d of slope km=f (k), Fig. 4 are different film thickness dmWith it is corresponding
Slope k between relation curve, therefore pass through the slope of curve k of differential values ΔΦ and incidence angle variation Δ θ, it may be determined that
The thickness of spr sensor institute metal-coated films.
The implementation steps of the present invention are as shown in Figure 5：Step 1：Selected incidence central angle θ0Value and incidence angle become
The value range of momentum Δ θ passes through theoretical calculation, when obtaining different-thickness, the pass of differential values ΔΦ and incidence angle variation Δ θ
It is curve, is fitted the slope k of the relation curve, and establishes thickness of metal film dmWith the corresponding theory relation curve of slope k,
Final fitting solves thickness of metal film dmWith the functional relation formula d of slope km=f (k)；Step 2：Set one group of incidence
Angular variable amount Δ θ values select initial incidence angle and change magnitude, make light beam 1 with θ0+ Δ θ, light beam 2 are with θ0The angle of-Δ θ can
It is set to symmetrical direction or the different position at the metallic film interface of prism-type spr sensor is incided into side direction；Step
Three：Incidence angle according to step 2 obtains prism-type spr sensor coating film area light beam 1 and 2 respective interference item of light beam
Print image；Step 4：Incidence angle according to step 2 obtains the non-coating film area light beam 1 of prism-type spr sensor and light beam
2 respective interference fringe images；Step 5：The light beam 1 and light beam 2 that step 3 and step 4 are obtained are in coating film area and non-plated
The interference image of diaphragm area is compared, calculates respectively, respectively obtain light beam 1 and light beam 2 coating film area TM polarized waves and
The phase changing capacity difference DELTA δ of TE polarized wavesr1With Δ δr2, by Δ δr1With Δ δr2Subtract each other, obtain differential values ΔΦ；Step 6：Root
According to step 2, change the value of Δ θ successively, and repeat step 3 to step 5, obtain one group and incident angle variation Δ θ phases
One group (Δ θ, ΔΦ) of gained is carried out curve fitting, and acquires the slope k of the matched curve by corresponding differential values ΔΦ；
Step 7：By the slope k of experiment curv obtained by step 6, the functional relation formula d in step 1 is substituted intomIn=f (k), you can
Determine the thickness of spr sensor institute metal-coated films
As shown in Figure 6, Figure 7, the embodiment of the present invention is by measurement laser 1, collimation lens 2, polarizer 3, is divided rib
Mirror 4, plane mirror 5, prism-type spr sensor 6, corner platform 701 and XYZ D translations guide rail 702, plane mirror 8,
9th, 10,11,12, interference system 13, polarizer 14, lens 15, what CCD16 and computer system 17 were formed.Prism-type SPR sensorgram
Device 6 can arbitrarily be adjusted in X, Y, Z-direction by the corner platform 701 of bottom belt XYZ D translations guide rail 702 and put down in XY
360 ° of rotations are done in face.
The specific measurement process of embodiment is as follows：By the laser that laser 1 is sent after collimation lens 2 and polarizer 3
The polarised light of polarization direction and the plane of incidence in 45 degree of angles is adjusted to, then is divided through Amici prism 4 for light beam 1 and light beam 2, light beam 1
The coating film area of 6 inclined edge surfaces of prism-type spr sensor is incided into from one side of prism 601 through speculum 5, light beam 2 is through speculum 8
Incide into the coating film area of 6 inclined edge surfaces of prism-type spr sensor from one side of prism 601, adjustment XYZ D translations guide rail 702,
Corner platform 701, speculum 8,9 make light beam 1 and light beam 2 with the original incident angle θ of selection0=43.9 degree incide into metal
On the interface of film 602, by adjusting speculum 12, the light beam 1 through metal film reflector is made to impinge perpendicularly on interference system 13
In, the reflected light of light beam 1 is first respectively divided into TM polarized waves 1, TE polarized waves 1 by polarization spectroscope 1301, by the reflected light of light beam 2
It is divided into TM polarized waves 2, TE polarized waves 2, after the outgoing of polarization spectroscope 1301, after the reflection of plane mirror 1302,1303
It is converged at polarization spectroscope 1304, is then in the polarizer 14 of 45 degree of angles by polarization direction and TM polarized waves direction of vibration
TM1 polarized waves and TE1 polarized waves, TM2 polarized waves and TE2 polarized waves is made to generate interference effect respectively, interference pattern is received by CCD16
Picture, then record by computer system 17 interference image of acquisition.After recording coating film area image, adjustment corner platform 701 and XYZ
Z-direction guide rail in D translation guide rail 702 makes incident light beam strikes to the non-plated film area of 6 inclined edge surfaces of prism-type spr sensor
Domain, observes the offset of interference image striped, and new interference image is recorded by computer system 17.
According to the principle of interference of light, when incident light is irradiated to non-coating film area with incidence angle θ, through interference system and polarization
After piece generates interference effect, interference light intensity I (0,0, θ) is represented by：
In formula, Ia(0,θ)、Ib(0, θ) light intensity of the two beam interferometer light after the reflection of non-coating film area is represented, k represents striped
Spatial variations frequency, Δ δr(0, θ) represent that the phase changing capacity of TM polarized waves and TE polarized waves is poor after the reflection of non-coating film area
Value, similarly, when incident light is irradiated to coating film area with incidence angle θ, after interference system and polarizer generate interference effect,
Interference light intensity I (dm1, θ) and it is represented by
In formula, I1(dm1,θ)、I2(dm1, θ) represent after coating film area reflects two beam interferometer light light intensity, k represent striped
Spatial variations frequency, Δ δr(dm, θ) and represent that the phase changing capacity of TM polarized waves and TE polarized waves is poor after coating film area reflects
Value.
The one-dimensional space position view of interference light intensity as shown in Figure 8 can be drawn according to above-mentioned formula, x in figure1
And x3The location of two adjacent bright fringes centers, x when incident light irradiates non-coating film area are represented respectively2Represent incident light
The location of bright fringes center when irradiating coating film area.Following relational expression can be derived by according to above-mentioned two formula and Fig. 6
kx1+Δδr(0, θ)=kx2+Δδr(dm, θ) and=kx3+Δδr(0,θ)-2π
If Δ h1=x2-x1Represent the offset of interference fringe in two width interference images, Δ h2=x3-x1Represent interference image
In adjacent interference fringe amount of space, then above formula be represented by
Δh1With Δ h2Value can be drawn by two width interference images by computer system processor, by known in embodiment
Laser output wavelength 632.8nm, BK7 Refractive Index of Glass Prism 1.51, the dielectric constant -10.7+0.8i of golden film, can calculate through
The phase changing capacity difference DELTA δ of TM polarized waves and TE polarized waves after non-coating film area reflectionr(0, θ), according to above-mentioned formula, so that it may
To obtain light beam 1 and light beam 2 the phase changing capacity difference DELTA δ of TM polarized waves and TE polarized waves after coating film area reflects respectivelyr1
(dm, θ) and Δ δr2(dm, θ), by Δ δr1With Δ δr2Subtract each other, obtain differential values ΔΦ.
Then corner platform 701 rotates Δ θ (rotate clockwise for positive value, rotate counterclockwise as negative value), light beam 1 and light beam
2 incidence angle changes Δ θ, and the direction only changed is on the contrary, i.e. light beam 1 will be with θ at this time0+ Δ θ, light beam 2 will be with θ0-Δθ
Angle incide into the metallic film interface of prism-type spr sensor, the slewing area of Δ θ is -0.1 °~0.1 °, change interval
0.01 °, the angle by adjusting plane mirror 10,11,12 makes light be propagated according to previous path, and records different Δ θ institutes successively
Corresponding interference image, and corresponding differential values ΔΦ is obtained, differential values ΔΦ value is thus drawn out with incident angle variation Δ θ
Experiment curv, and fit slope of a curve k, bring gained k values into formula dm=f (k), you can determine spr sensor
The thickness of institute's metal-coated films.
The method of the invention be not limited in measure golden film thickness, the metal types that can be measured include gold, silver,
Copper, aluminium, platinum, titanium, nickel, chromium metallic film, measurement thickness are no more than 100nm, and measurement resolution is higher, can reach 0.1nm.
This method belongs to non-contact measurement method, and metallic film will not be caused to damage in measurement process.
Claims (8)
1. it is a kind of for measuring the SPR differential phae measuring methods of nanoscale double-layer metal film thickness, it is characterized in that：Step is such as
Under：
Step 1：Establish thickness of metal film dm and the functional relation formula of slope k：The formula is according to selected incident angular variable
Measure the value range of Δ θ and the value of incident central angle θ 0, calculate when obtaining each thickness, one group with by incidence angle variation Δ θ
This group of incidence angle variation Δ θ is drawn for independent variable, by dependent variable of corresponding differential values ΔΦ and corresponds to differential values Δ
The relation curve of Φ is fitted the slope k of this relation curve, establishes thickness of metal film dm and the corresponding theory relation of slope k
Curve, and be fitted and solve thickness of metal film dm and the functional relation formula dm=f (k) of slope k；
Step 2：According to the value range of the incidence angle variation Δ θ described in step 1, within its scope, one group of setting enters
Firing angle variation Δ θ values, and one group of incidence angle is changed in magnitude herein, is selected a value as initial incidence angle and is changed magnitude, light
Beam 1 incides into the metallic film interface of prism-type spr sensor with θ 0+ Δs θ, light beam 2 simultaneously with the angle of θ 0- Δs θ；
Step 3：Incidence according to step 2, obtains prism-type spr sensor coating film area light beam 1 and light beam 2 is each
From interference fringe image；
Step 4：Incidence according to step 2 obtains the non-coating film area light beam 1 of prism-type spr sensor and light beam 2
Respective interference fringe image；
Step 5：The light beam 1 and light beam 2 that step 3 and step 4 are obtained are in the interference image of coating film area and non-coating film area
It is compared, calculates respectively, respectively obtain light beam 1 and light beam 2 and become in the TM polarized waves of coating film area and the phase of TE polarized waves
Change amount difference DELTA δ r1 and Δ δ r2, Δ δ r1 and Δ δ r2 are subtracted each other, obtain differential values ΔΦ；
Step 6：According to step 2, change the value of Δ θ successively, and repeat step 3 to step 5, obtain one group and incidence angle
The corresponding differential values ΔΦs of variation Δ θ are spent, one group (Δ θ, ΔΦ) of gained is carried out curve fitting, and acquires the fitting
Slope of a curve k；
Step 7：The slope k of experiment curv obtained by step 6 is substituted into the functional relation formula dm=f (k) in step 1,
It can determine the thickness of spr sensor institute metal-coated films.
2. it is according to claim 1 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：Incident 0 values of central angle θ of the step 1 are within SPR resonance angle ± 1 °, the incidence angle variation of the step 1
The value range of Δ θ is -0.1 °~0.1 °；The different metal film thickness dm of the step 1 corresponds to differential values ΔΦ and incidence
The theory curve basic parameter of the slope of curve k of angular variable amount Δ θ is：1. incident angle θ 0,2. incidence angle variation
The incident light of the permittivity ε m of Δ θ, 3. Refractive Index of Glass Prism np, 4. metallic film, 5. the permittivity ε a, 6. laser of air
Wavelength X；The step 2 makes light beam 1 incide into prism-type spr sensor with θ 0+ Δs θ, light beam 2 with the angle of θ 0- Δs θ
Metallic film interface, refers to plated film area of the hot spot part in spr sensor of light beam 1 and light beam 2, and a part is in SPR
The non-plated film area of sensor, and the hot spot of light beam 1 and light beam 2 is incident to the different position at interface；The step 3 is by light beam
1st, light beam 2 incides into the reflected light of prism-type spr sensor coating film area and is respectively divided into TM1 polarized waves and TE1 polarized waves, TM2
Polarized wave and TE2 polarized waves, TM1 polarized wave of the light beam 1 using in reflected light are used as measurement light, TE1 polarized waves with reference to light, light
TM2 polarized wave of the beam 2 using in reflected light is used as measurement light, TE2 polarized waves with reference to light, then, the TM1 of light beam 1 is made to polarize
Ripple and TE1 polarized waves generate interference fringe after interference system and polarizer, make the TM2 polarized waves of light beam 2 and TE2 polarized waves warp
Interference fringe is generated after interference system and polarizer, records two interference images respectively；The step 4 is to enter light beam 1, light beam 2
Be mapped to the non-coating film area of prism-type spr sensor reflected light be respectively divided into TM1 polarized waves and TE1 polarized waves, TM2 polarized waves and
TE2 polarized waves, TM1 polarized wave of the light beam 1 using in reflected light are used as measurement light, TE1 polarized waves with reference to light, and light beam 2 is with anti-
The TM2 polarized waves in light are penetrated as measurement light, TE2 polarized waves are used as with reference to light, then make the TM1 polarized waves of light beam 1 and TE1 inclined
Vibration wave generates interference fringe after interference system and polarizer, make light beam 2 TM2 polarized waves and TE2 polarized waves through interference system
With interference fringe is generated after polarizer, record two interference images respectively；The step 5 is to obtain step 3 and step 4
The coating film area of light beam 1 and light beam 2 is compared, calculates and handles with the interference image of non-coating film area respectively, respectively obtains
In two width interference images of light beam 1 and light beam 2 in the offset of interference fringe and interference image adjacent interference fringe amount of space,
Thus the TM1 polarized waves of coating film area light beam 1 and the phase changing capacity difference DELTA δ r1 of TE1 polarized waves and plated film area are calculated
The TM2 polarized waves of domain light beam 2 and the phase changing capacity difference DELTA δ r2 of TE2 polarized waves, Δ δ r1 and Δ δ r2 are subtracted each other, obtain difference
Dynamic value ΔΦ.
3. it is according to claim 2 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：The interval of one group of incidence angle variation Δ θ value of setting of the step 2 is at least 0.02 °.
4. the SPR differential phae measuring methods for being used to measure nano level metal film thickness according to Claims 2 or 3,
It is characterized in that：The step 3 incides into the reflected light of prism-type spr sensor coating film area, is passed to incide into prism-type SPR
The light at sensor prism-metallic film interface；The step 4 incides into the reflection of the non-coating film area of prism-type spr sensor
Light, to incide into the light of prism-type spr sensor prism-Air Interface；The step 6 is from initial incidence angle variation Δ θ
Start, change the value of incident angle variation Δ θ successively, variation order should be according to one group of incidence angular variable set by step 2
Amount；The step 7 is by the slope k of experiment curv obtained by step 6, substitutes into the theory function relation formula given by step 1
Dm=f (k) determines the thickness of spr sensor institute metal-coated films.
5. it is according to claim 1 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：The metallic film is gold, silver, copper, aluminium, platinum, titanium, nickel, chromium metallic film.
6. it is according to claim 4 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：The metallic film measurement thickness range is 0-100nm, measurement resolution 0.1nm.
7. it is according to claim 1 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：Light beam 1 described in step 2 with θ 0+ Δs θ, light beam 2 with θ 0- Δs θ can be set to symmetrical direction or with side direction simultaneously
Incide into the different position at the metallic film interface of prism-type spr sensor.
8. it is according to claim 1 for measuring the SPR differential phae measuring methods of nano level metal film thickness, it is special
Sign is：The step 2 makes light beam 1 incide into the metal of prism-type spr sensor with the angle of θ 0- Δs θ with θ 0+ Δs θ, light beam 2
Film interface is two-beam or multi-beam.
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